How can I create a crashing wave effect?
A simple solution to get you started is to use a particle system and the smoke simulator.  Initial testing on my end used a camera set high on the Z axis facing down to the emitter object within the smoke domain.  Track the smoke within the domain to the particle system.  Emit for about 20 frames with a lifetime of 20 on the particles. the object I used was an icosphere cut in half with the rounded side facing the positive Z axis also the object emitted from the faces.  Under Emitter velocity, I set the Normal to 15, initial velocity on the particles per axis at X &amp; Y = 0, Z = 5.  As the particles move out from the emitter, the smoke will follow their path.  As for the crashing of the waves exploding onto the dock, use an object within the domain as both a particle obstacle and a smoke collision object under the physics tab.  Within whatever render setting you should be able to control the material and or color of the smoke to simulate water and foam.  Run the animation and tweak to your needs. Hope this helps.